where and how to use Page.RegisterRequiresViewStateEncryption()?

I would like to know how to register a control with viewState encryption. The syntax of Page.RegisterRequiresViewStateEncryption()开发者_如何转开发 method does not indicate particular control other than the page object. Provide a sample code to answer this question would be very helpful.

RegisterRequiresViewStateEncryption() is to be used with the ViewStateEncryptionMode property of the Page object. That property supports three values:

• Always: The page's view state will always be encrypted.
• Never: The page's view state will never be encrypted, even if RegisterRequiresViewStateEncryption() is called by a control or the page itself.
• Auto: The page's view state will be encrypted only if RegisterRequiresViewStateEncryption() is called by a control or the page itself.

So, if you call Page.RegisterRequiresViewStateEncryption() from, say, one of your control's OnLoad() method, or from the OnLoad() method or Page_Load event of your page, the view state will be encrypted, unless your page's ViewStateEncryptionMode property is set to Never.

The first link above contains a code sample that enables view state encryption on postback if the end user chose to retrieve sensitive information.